Can you explain the meaning of <T = MyType>?

Question

Can you explain the meaning of <T = MyType>?

While exploring a TypeScript file, I stumbled upon this interface declaration:

interface SelectProps<T = SelectValue> extends AbstractSelectProps { /* ... */ }

I've searched through the TypeScript handbook for <T = but couldn't find any mention of it in the sections on Generics or Advanced Types, nor on the what's new in TypeScript page.

I'm familiar with <T extends ...> from the documentation, but this is my first time encountering <T = ...>.

Does anyone know what this construct is called? What does it signify? And how does it differ from using = versus extends?

typescript generics

Answer 1

Answer №1

T = Whatever introduces a fresh concept in generics, enabling users to define a default type without requiring them to specify one (if they opt for the default).

For more information, check out this resource and this page.

Here's an example to illustrate:

abstract class Component<Props = {}, State = {}> {
  // ...
}

// Only specify the first generic for Props, leaving State as {}
class MyComponent extends Component<{foo: string}> {
  // ...
}

Answer 2

T = Whatever introduces a fresh concept in generics, enabling users to define a default type without requiring them to specify one (if they opt for the default).

For more information, check out this resource and this page.

Here's an example to illustrate:

abstract class Component<Props = {}, State = {}> {
  // ...
}

// Only specify the first generic for Props, leaving State as {}
class MyComponent extends Component<{foo: string}> {
  // ...
}

Can you explain the meaning of <T = MyType>?

Answer №1

Similar questions

select items using a dropdown menu in an Angular application

Regular Expressions: Strategies for ensuring a secure password that meets specific criteria

Ways to provide information to an rxjs observer

Discovering all the specifics of a data type within VSCode's popup feature by hovering over a variable

Ways to attach an event listener to a useRef hook within a useEffect hook

Excluding Layout from Display on Certain Pages in a Next.js 13 App Router

Is there a way to determine if a React functional component has been displayed in the code?

Utilize Knex to retrieve data from the req.query

The onClick event in HostListener is intermittent in its functionality

Using Typescript to enclose the object and selectively proxying a subset of its methods

Visual Studio fails to acknowledge changes made to TypeScript files and incorrectly assumes that the project is up to date

Adjust the appearance of matSelect when the selection menu is activated

The 'path' property is not found on the 'ValidationError' type when using express-validator version 7.0.1

Can you provide guidance on effectively utilizing a Pinia store with Vue3, Pinia, and Typescript?

TypeScript and Express create a powerful array combination capability within the type system

What is the best way to call an Angular component function from a global function, ensuring compatibility with IE11?

Getting a file object with v-file-input in Nuxt.js

Is it possible to link multiple references to a single Element/Node?

The element 'mat-toolbar' is unrecognized and not known:

Angular does not recognize the boolean variable